The present invention relates to a selector system for controlling the movement of elevator cars. In particular, the present invention is an elevator having an improved digital selector system.
Digital selectors possess many advantages over the mechanical selectors used in the past, and are for such reason preferred in many types of modern elevator installations. Known digital selectors include a device that generates pulses indicative of a given increment of car motion, such as 0.01 foot. A reversible counter stores, as a binary number measured in units of the same incremental distance (for example, 0.01 feet), the instantaneous car position relative to an arbitrary zero position, such as the lowest landing served. As the car moves and pulses are generated, the pulses are supplied to the reversible counter, which adds or subtracts pulses from the count, depending upon the direction of car movement, to change the stored car position.
The elevation of each floor is stored in memory as a binary number representing the distance from the same zero reference to the particular floor, measured in the same increments of distance (0.01 foot, in this example) as the instantaneous car position. The digital numbers representing floor elevation, and the digital number representing instantaneous car position, can then be manipulated by a microprocessor or other solid state control to perform normal selector functions, such as direction selection and call pick-up and cancelling, and provide position indicators and other signals and the position-controlled slowdown signals.
The most common problems encountered with digital selectors are those caused by spurious electrical noise, which can change the count in the reversible counter, and those caused by power interruptions, which can cause a total loss of count. When such occurs, the stored value representative of elevator car position is erroneous and remains so until corrected, which can usually only be done by sending the car back to ground floor level to reset the counter to zero. Many solutions have been proposed to detect such failures and correct the count without resorting to sending the car back to the lowest landing. However, it would be desirable to minimize or eliminate this problem.
There are also many known methods for controlling the starting, stopping, and floor selection functions of the elevator car. It would be desirable to provide a readily programmable processing system to control these functions with selectable inputs and operating parameters.